The invention is based on an air flow rate meter as defined hereinafter. In a known air flow rate meter, to prevent the particles floating in the air from being deposited on the substrate, the faces facing into the flow are as small and rounded as possible, to keep the amount of deposits collecting there during air flow rate meter operation minimal. Such deposits not only affect the flow course in the vicinity of the substrate, but also cause poorer thermal behavior of the air flow rate meter, making the air flow rate meter thermally more sluggish by slowing down the measurement speed as the air flow rate varies. Nor are the precautions taken in the known air flow rate meter capable over the long run of preventing such deposits, so that the aforementioned kind of undesirable change in the characteristic curve of the air flow rate meter eventually occurs.